Electric brake



F. MCCURTAIN Mmh 21, 195o.

ELECTRIC' BRAKE Filed -March 28L 1947 Q M Nm. m mw m. NNN

Inventor RANK/14660,? mf,

gLf--AF MAJ/IJ- Cttorneg Patented Mar. 21, 1950 ELECTRIC BRAKE FrankMcCurtain, Los Angeles, Calif., assigner to Wendell R. McKenzie,Montebello, Calif.

Application March 28, 1947, Serial No. 737,775

Claims.

` The present invention relates to electric brakes' in general andparticularly to an electric brake for ambulatory vehicles such asautomotive trucks, railway cars, etc. More specifically they inventioncomprises an operator-controlled electrical brake adapted to absorb thebraking load of a heavy vehicle over an extended time period, as forexample, when descending a long grade, and which is particularlycharacterized in that the braking unit is clutched gradually into xedrelationship to the load.

The provision of adequate braking power upon heavy high-speed ambulatoryvehicles is of tremendous importance. The ability to brake a moving caror truck within reasonable time and distance limits governs, in manyinstances, maximum speeds. The power required to brake the speed of amoving vehicle Within a certain distance and time is exactly equal tothe power required to accelerate the vehicle to the same speed Withinthe same limits. It is necessary, however, not only to provide for safeand positive braking of a particular rating but it is also necessary toinsure that the braking apparatus will be capable of performingcontinuously through extended time periods. The long inclines found uponmany highways and road beds provide a problem which too frequentlyordinary braking means are not capable of handling satisfactorily. Theordinary brakes of large 'capacity working through friction brake shoesmust dissipate the energy absorbed in the form of heat and, althoughmade of proper materials and properly designed, they frequently areincapable of handling the continued loads which they are called upon toassume. In automotive vehicles where non-metallic linings are provided,all too frequently the lining is completely burned out, while in railwaycars fires sometimes result.

The provision of an electrical brake is an ideal solution where thepower must be dissipated over extended periods of time. The drivingenergy provided by the moving vehicle is translated into electro-motiveforce which drives electric current through a suitably cooled resistanceand by which the power is absorbed. So long as the heat-dissipatingcapacity of the resistance is adequate the extension of the time periodis unimportant. When the brake in the form of an electrical generatingunit is directly connected to a rotating part of the vehicle so that itat all times rotates there is unnecessary wear and deterioration. In theimproved electrical brake apparatus constructed in accordance with thepresent invention the braking means It is another object of theinvention to provide an electrical braking unit normally de-clutchedfrom the vehicle to be braked and which isv gradually brought up to fullspeed before being loaded.

A further object of the invention is to provide an electric brake forambulatory vehicles in which the normally inoperative electrical brakeis iirst brought up to speed before being positively connected to therotating part to be braked, and thereafter the braking action isadjusted by the selective adjustment of a variable resistance elementunder the control of the operator.

These and other more specific objects' will appear upon reading thefollowing specification and claims, and upon considering in connectiontherewith the attached ydrawing to which they relate.

Referring now to the drawing in which pre ferred embodiments of thepresent invention `are illustrated, and in which the same referencecharacter refers to the same parts throughout:

Figure 1 is a view of a preferred embodiment of the invention in whichcertain parts are shown mechanically and other related parts diagrarmmatically;

Figure 2 is a diagrammatic view of a modied electrical power-dissipatingunit adapted to be substituted for the electrical unit of the firstembodiment shown in Figure 1; and

Figure 3 is a third embodiment illustrating an electricalcurrent-generating and heat-dissipating unit adapted to be substitutedin the Figure 1 construction.

In the drawing the invention is illustrated as embodied in an ambulatoryvehicle such as a truck comprising the usual parts of which only thosenecessary for an understanding of the pres ent invention will bereferred to specically. A transmission I2 is positioned immediately inthe rear of the motor proper ll, its gears being se lectively controlledby a manually operable shift lever I3. The drive shaft I4 extendsrearwardly from the transmission and, in the manner of the usualautomotive vehicle, may be connected to the driving wheels. It is to beunderstood that the drive shaft I4 is to be considered as illustrativein that it may be any rotating part of an ambulatory vehicle directlyconnected to the rotating carrying wheels and rotatable upon therotation thereof.

The electrical power-generating and heatdissipating unit is illustrateddiagrammatically in Figure 1, being indicated by the reference characterI6, and is connected to and driven by the shaft I4 through apower-transmitting and clutching unit, indicated generally by thereference character I'I. The electrical unit IS is normally inoperativeand is conditioned for braking operation only upon being connected tothe drive shaft I4 by the clutching unit I 1 which will now bedescribed.

A cylindrical casing I8 is rotatably supported by a bearing I9 upon thereduced end 2I of the casing of transmission I2. A flat disc clutchplate 22 carrying a brake lining material 23 upon its rearward face isfixed within casing I8 for rotation therewith, being spaced by aninternal shoulder 24 from the outer race of bearing I9. The rearwardopen end of casing I8 is provided with xed longitudinally extending gearteeth 26, concentric to shaft I4, the entire construction being fixedlongitudinally relative to the shaft.

To bring the cylindrical casing I8 up to the speed of the rotary shaftI4 by cooperation with clutch plate 22 clutch plate 21 is positionedwithin casing I8 in normal spaced relationship to that plate. Plate 21is keyed at 28 to shaft I4 for relative longitudinal sliding movementand is provided upon its face adjacent plate 23 with a lining material2S. Rearwardly of casing I8 a longitudinally slidable non-rotatablecollar 3| encircles shaft I4, being suitably connected, so as to be ableto shift axially in either direction to a circular plate 32, keyed toshaft I4 for sliding movement. Plate 32 is provided on its forward facewith circularly arranged teeth adapted in the forward position of collar3| to mesh with the teeth 2E on casing I8. A strong coil spring 34spaces plate 32 from movable clutch plate 21, being connected at itsends to the plates. An actuating lever 36 is pivoted to a suitablesupporting structure of vehicle I0, its slotted lower end beingconnected at 38 by a radially extending pin to collar 3|. Lever 36 ispositioned in the vehicle as to be conveniently controlled by theoperator and is adapted to tudinally upon shaft I4 and by such movement,and with the cooperation of coil spring 34, to move the clutch plate 21from its inoperative position, illustrated in Figure 1, forwardly andinto engagement with the clutch disc 22 fixed to casing I8.

This relationship of the clutch plate 21 to plate 22 and of the opposedteeth 25 and 33 is such that initial contact is made in the clutchingoperation by the lined surfaces of the clutch elements 22 and 21. Afterinitial driving contact, and as the operator-actuated lever 35 isfurther pivoted, the spring 34 is compressed, the continued movement ofplate 32 advancing the teeth 33 toward the teeth 26. The compression ofspring 34 places a greater force upon the movable clutch plate 21 toforce it more firmly against the xed plate 22 and results in anaccelerated clutching action. By the time spring 34 is sufficientlycompressed by the forward movement of plate 32 as to bring teeth 33 intomesh with the casing-carried teeth shift collar 3I longi- 26 the casingI8 is rotating at the speed of rotation of the shaft I4 and a directdriving relationship is established without clashing.

The rotative force of the cylindrical casing I8, now rotating at thespeed of the shaft I4, is transmitted to the electrical braking unit I6by suitable power-transmission means comprising a gear 4I xed exteriorlyupon casing I8 and transmitting power through a chain 42 to a pinion 43xed upon a shaft 44 which rotates with the rotor A of the unit generatorG.

Directing attention specifically to electrical unit I6, it is seen tocomprise a generator G formed of a rotor A and a stator winding Ws. Anoperator-controlled variable resistance Rv is connected by a lead 5I toarmature A at one of its Slip rings While a second lead 52 connects arectier 53 to the second slip ring. Leads 56 and 51 extend from thevariable resistance Rv and the rectifier 53, respectively, and connectto leads 58 and 59, respectively, leading to stator winding Ws. Thecurrent through the armature A is rectified by rectifier 53 and analternating current is generated upon armature rotation in statorwinding Ws. The latter is connected through leads 58 and 59 to leads 5Iand 82, respectively connecting to the opposite sides of the loadresistance RL. Clearly adjustment of variable resistance Rv varies thecurrent in the rotating field which in turn controls the currentgenerated in the stator winding Ws and so the current which flowsthrough the resistance RL.

As the entire apparatus is mounted upon an ambulatory vehicle themovement of the air relative to the vehicle itself may be relied uponfor the removal of heat from resistance RL. Under certain extremeconditions, however, it may be expedient to supplement this readilyavailable heatremoving air stream. In such an event a motor fan unit isprovided, comprising an air-moving fan 66 driven by a motor 61 connectedby leads 68 and 69 to the leads 6I and 62 connecting to the statorwinding Ws. As motor 61 will vary in its speed directly with thefrequency of the curl' rent generated in stator winding Ws it followsthat its speed will vary with the speed of rotation of armature A and sowith the load which is placed upon the unit.

The operation of the invention constructed in accordance with the firstdescribed embodiment 1s as follows. In proceeding normally and withoutneed for braking action the clutch unit I1 is open and the clutch plates22 and 21 are spaced in the manner shown in Figure 1. Cylindrical casingl 8 remains standing and the shaft I4 rotates relative thereto. It beingdesired to brake the vehicle, as during the descent of a long grade, thedriver pulls rearwardly upon operating lever 36, whereupon the lower endthereof connected to the clutch collar 3| forces that collar and theattached plate 32 forwardly. The movement o! the latter is transmittedthrough the strong coil spring 34 to the movable clutch plate 21 whichis also longitudinally slidable upon driving shaft I4 with which itrotates. Friction lining 29 on movable clutch plate 21 makes contactwith the lining 23 upon plate 22 and as the pressure between the platesincreases, the collar 3| being Imoved forwardly by the lever 36, thedriven plate 22 is brought up to speed and with it the cylindricalcasing I8 to which it is fixed. By the time the collar 3I has beenadvanced sufficiently to compress the coil spring 34 to a point whichenables the gear teeth 33 to mesh with the casingcarried teeth 26, thecasing I8 and the shaft I4 are rotating at synchronous speeds. l

The rotation of the clutch casing I8 is transmitted, as previouslydescribed, through the gear. 4I, chain 42, and pinion 43 to the shaft 44which rotates with, or may in fact be the shaft of the generator` G. Inany event rotation of shaft 44 effects the rotation of armature A whichhas sufiicient residual magnetism to initiate the generation of current.If necessary, however, a flash energization of the armature winding maybe provided by any suitable and usual means, such as, for example, thebattery of the vehicle. Current generated in the rotor A is controlledby the variable resistance Rv so that the extent of the braking actionis under `the direct control of the operator. 'I'he rotor current isrectified in rectifier v53 but an alternating current is generated inthe stator winding Ws. The latter is loaded by the resistance RL,connected thereacross, the current generated being converted into heatand dissipated to the air through which the vehicle moves. As described,additional heat removal ability may be provided by a fan as actuated bythe motor 61 connected across the winding Ws.

So long as it is desired to brake the vehicle the unit I6 remainsconnected and continues to provide a braking power by the generation ofcurrent to an extent determined by the position of Rv. Preferably,before opening the clutch unit I'I at the end of the braking period, theoperator will return the resistance unit Rv to zero position so that theclutch unit will be transmitting a minimum force. The relationship isone in which the electrical power-absorbing unit can be brought up tospeed before being loaded, if desired, and in all events is at fulldriving speed before being positively and directly connected by theintermeshing gears.

Referring now to Figure 2 in particular, a second preferred modificationof the invention is illustrated in part and is in all respects, exceptthose hereinafter specified, identical to the first describedembodiment. The distinctions present reside in the current-generating,load-absorbing unit illustrated, which is again generally indicated bythe reference character I6. As in the first embodiment the shaft 44 isclutched to the drive shaft :I4 of the vehicle to be braked and itselfserves to drive the generator rotor. The latter is indicated by thereference character A2 and comprises a plurality of poles formed bypermanent magnets of high intensity `and strength. Windings, indicatedby the reference character 16, are wound upon the poles, being connectedto the rotor slip rings and through them to external leads Il and 1-8for the purpose of enabling the permanent magnets to be rem-agnetized atintervals and as required. No other electrical connections are made tothe armature. The stator winding is indicated by the reference characterWsz and is connected by leads IiI and -82 to the variable resistanceRvz. In all other respects this embodiment of the invention is identicalto that rst described.

The operation of this second preferred embodiment of the invention isidentical to the first embodiment except as to the electrical operatingcharacteristics. Here the rectifier of the first embodiment has beeneliminated and the permanent magnets of the rotor A2 are relied upon toprovide the magnetic field necessary to generate current in the statorwinding Wea. The current generated in that winding is conducted throughleads 8I and 82 to the variable resistance Rv:

which is adjustable under the control of the:

Referring now to Figure 3, a third preferred:

embodiment of the invention is partially illustrated, which, in themanner of the disclosure of Figure 2, is adapted to be substituted forthe electrical unit I6 in the embodiment of Figure l. Again theelectrical current-generating and power-absorbing unit is indicatedgenerally by the reference character I6, and the rotor A: is connectedto and driven by the shaft 44, connected as previously described. Thestator winding, here indicated by Wsa, has current generated in it bythe rotation of the rotor A3, the current passing through conductors 86and 81 to the resistance Rm to be dissipated in the form of heat as inthe Vpreceding embodiments. present instance, however, the braking load,as indicated by the stator current, is controlled by a variableresistance Rvs connected in series by leads 88 and 89 to the rotor A3and to an exciter generator 9 I. The latter is also connected to therotor A3 through a third lead 92. Exciter generator v9| is also drivenby shaft 44 from the drive shaft I4 and generates a direct currentproportionalin magnitude to its speed of rotation, subject to thecontrol of the manually operable variable resistance Rvs. Thisparticular construction has the advantage in load adjustment in that theexciting current to be varied is of much smaller magnitude than the loadcurrent.

The operation of this third preferred embodiment of the invention issimilar to that previously described. The clutching operation isidentical to that of the first embodiment and the current generated inthe stator `winding Wss is proportional to the speed of rotation of therotor A3, determined' by the speed of rotation of the shaft 44 and so ofshaft I4, and is also proportional to the excitation current provided bythe exciter 9| under the control of the loperatorcontrolled resistanceRvs. As in the previous embodiment the load current in the winding Wssisabsorbed in the resistance Rm and dissipated in the form of heat tothe surrounding air. As

in the first and second embodiments a motor-y driven fan, as illustratedin the first embodiment, may be included for the resistance ifpreferred.

While the particular apparatus herein shown and described in detail isfully -capable of attaining the objects and providing the advantageshereinbefore stated, it is to be understood that it is merelyillustrative of the presently preferred embodiments of the invention andthat no limitations are intended to the details of construction ordesign herein shown other than as defined in the appended claims.

I claim:

1. In combination in an ambulatory vehicle of the type including adriving motor and a drive shaft connected thereto, brake means to brakesaid vehicle comprising an electric generator, means to load saidgenerator to vary the braking effect, a casing enclosing said shaft andmounted for independent rotation relative thereto, powertransmittingmeans connecting said casing to said generator, and means to bring saidcasing up to synchronous speed with said shaft comprising a frictionclutch member fixed to said casing and rotatable therewith, a secondfriction clutch member xed to said shaft for rotation therewith andlongitudinally slidable thereon, manually operable means to adjust saidsecond clutch member In thel anon-:o1

7 into and from frictional engagement with said friction clutch member,and cooperating .positively engaging means on said shaft and on saidcasing engageable after said friction members are in full engagement tolock said shaft and said casing together.

2. The construction recited by the preceding claim characterized in thatsaid means to load said generator are adjustable independently of saidclutch whereby said generator may be loaded after being clutched to saidshaft to reduce the load upon the clutch.

3. In combination in an ambulatory vehicle of the type including adriving motor and a drive shaft connected thereto, means to brake saidvehicle including an electric generator having a wound rotor, a woundeld connected to said rotor, and a rectifier and a variable resistancein series with said rotor winding to provide a direct-current for saidfield and to vary the load, respectively, a casing enclosing said shaftand mounted for independent rotation relative thereto,power-transmitting means connecting said casing to said generator, andmeans to bring said casing up to synchronous speed with said shaftcomprising a friction clutch member fixed to said casing and rotatabletherewith, a second friction clutch member fixed to said shaft forrotation therewith and longitudinally slidable thereon, manuallyoperable means to adjust said second clutch member into and fromfrictional engagement with said friction clutch member, and cooperatingpositively engaging means on said shaft and on said casing engageableafter said friction members are in full engagement to lock said shaftand said casing together.

4. In combination in an ambulatory vehicle of the type including adriving motor and a drive shaft connected thereto, means to brake saidvehicle including an electric generator having a permanent magnetrotating field with a remagnetizing winding, and a stator winding loadedby a variable resistance to vary the braking effect, a casing enclosingsaid shaft and mounted for independent rotation relative thereto,powertransmitting means connecting said casing to said generator, andmeans to bring said casing up to synchronous speed with said shaftcomprising a friction clutch member fixed to said casing and rotatabletherewith, a second friction clutch member fixed to said shaft forrotation therewith and longitudinally slidable thereon, manuallyoperable means to adjust said second clutch member into and fromfrictional engagement with said friction clutch member, and cooperatingpositively engaging means on said shaft and on said casing engageableafter said friction members are in full engagement to lock said shaftand said casing together.

5. In combination in an ambulatory vehicle of the type including adriving motor and a drive shaft connected thereto, means to brake saidvehicle including an electric generator having a wound rotor energizedby an exciter driven by the rotor shaft, and a wound stator loaded by avariable resistance to vary the braking load, a casing enclosing saidshaft and mounted for independent rotation relative thereto,power-transmitting means connecting said casing to said generator, andmeans to bring said casing up to synchronous speed with said shaftcomprising a friction clutch member fixed to said casing and rotatabletherewith, a second friction clutch member fixed to said shaft forrotation therewith and longitudinally slidable thereon, manuallyoperable -means to adjust said second clutch member into and fromfrictional engagement with said friction clutch member, and cooperatingpositively engaging means on said shaft and on said casing engageableafter said friction members are in full engagement to lock said shaftand said casing together.

FRANK MCCURTAIN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 258,968 Wilkinson June 6, '18821,423,631 Scaife July 25, 1922 1,510,892 Kobayashi Oct. 7, 19241,677,633 Harrison July 17, 1928 2,052,788 Miller Sept. 1, '19352,317,254 Cowin Apr. 20, 1943

